"It all depends." (I know how infuriating that is).
If all you are doing is writing letters in Word and working with spreadsheets in Excel then 64MB would probably be fine and 128 is certainly more than enough.
Win 95 actually slowed down with too much RAM, but the newer the software the more it will benefit from more RAM. And if you are into large graphics or movie editing/viewing then even 256MB isn't over the top.
Why else would the serious users have multiple processors and Gigabytes of RAM.
When RAM is working to capacity, excess data and even program code is swapped out to the virtual RAM on your hard disk. This is the Pagefile.sys or win386.swp file you will find in your root directory or the Windows directory. This file needs to be at least as big as your RAM so that a complete "RAM full" can be paged out to the HDD. Mostly we leave the size of this file to Windows. You should not try to economise on a HDD which is filling up with rubbish by fixing this file to too small a size.
I have 256MB of RAM because I do a lot of graphics. For you, 128MB is probably fine. If your PC is unacceptably slow, and the rest of the kit is up to scratch, the you are going to have to look elsewhere.
I hope you are running a modern suite of applications. Memory management is vested in the application software. I haven't tried it but I would imagine that Office 97 running on Windows 2000 might not live up to expectations.
For example, Old WordPerfect used to run well on DOS on an Amstrad 8086 with 8MB RAM and 20MB hard drive. When I upgraded to a 386 with 32MB RAM and a 300MB HD (remember when that was the cutting edge?) WordPerfect came to a grinding halt in DOS while I could run Windows 3.11 perfectly well.
Not surpising that we keep chasing our tails in IT!
You want to see how the big boys do it, check out this link:
http://www.top500.org
[This message has been edited by fobotcso (edited 05 January 2001).]